1. Field of the Invention
The present invention relates to a hard-coated antiglare film, a polarizing plate and an image display including the same, a method for producing the same, and a method for evaluating the same.
2. Description of Related Art
With technical improvements in recent years, liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), and the like have been developed in addition to conventional cathode ray tube (CRT) displays as image displays and have been used in practical applications. Particularly, with technical innovations of LCDs with respect to, for example, wide viewing angles, high resolution, high response, and superior color reproduction, applications of LCDs are spreading from notebook personal computers (notebook PCs) and monitors to television sets. In an LCD, generally, a liquid crystal panel is used in which polarizing plates are disposed on both sides of a liquid crystal cell, respectively. Generally, in order to prevent scratches on the polarizing plate, the surface of the liquid crystal panel is subjected to hard coating treatment. For the hard coating treatment, a hard-coated film is often used. The hard-coated film is subjected to antiglare treatment to prevent a decrease in contrast due to a reflection of external light such as fluorescent light and sunlight as well as a reflection of an image at the surface of the liquid crystal panel. Particularly with an increase in size of the screens of image displays, the number of image displays equipped with hard-coated antiglare films is increasing.
Recently, in order to improve image quality, the number of high definition image displays with small pixel sizes and full HD (high definition)-capable image displays is increasing, and notebook PCs and monitors have the number of pixels of 140 ppi or more, and have high definition. In such high definition image displays, when a conventional hard-coated antiglare film is disposed, variations in brightness in pixels are emphasized which to cause a visible failure (a failure due to glare) and result in considerably deteriorated image quality. Conventionally, in order to produce an antiglare laminate that allows high definition to be provided, a method has been employed in which the haze value of the antiglare layer is increased to eliminate glare. However, this method has a problem in that the contrast is decreased considerably because light is scattered intensively at the panel surface. Furthermore, in the case where the surface unevenness is increased to improve antiglare properties, there is a problem in white blur in an oblique direction, that is, white blur is observed due to excessively intensive scattering of reflected light when the panel surface is viewed from the oblique direction. In the antiglare treatment, a method in which an uneven shape of the film surface is produced by adding, for example, inorganic or organic particles is used. Generally, although an improvement in antiglare properties and an improvement in contrast or white blur are considered to have a contradictory relationship, various proposals have been made to obtain both these properties. For example, it is being studied that aggregates with three-dimensional structures formed of the aforementioned particles are present in an antiglare layer (for instance, see JP2005-316413 A, JP2007-264113 A, and JP2007-249191 A). This, however, may cause scatter at the aggregates or may cause a fine pattern to appear in a hard-coated film. Furthermore, although a method that is effective in improving a part of properties has been proposed (for instance, see JP2003-4903 A, and JP4001320 B), a method that is effective in solving all the three problems described above has not been found.